Automatic telephone system



O. A, FRIEND. ET AL AUTOMATIC TELEPHONE SYSTEM Filed oct. 24, 1925 Patented Lug. 23, 1927.

UNITED STATES OTTO A. FREND, OF NEW YORK, N. Y., rAND GEORGE DUSTIN, OF WOODCLIFF, NEW JERSEY, ASSIG'NORS TO AMERICAN TELEPHONE AND TELEGRAPI-I COMPANY, A

CORPORATION 0F NEW YORK.

AUTOMATIC TELEPHONE SYSTEM.

Application Ied October 24, 1923. Serial No. 670,558.

This invention relates to automatic tele phone systems and more particularly to large multi-office automatic systems.

The object is a new and improved trunhing arrangement for systems in which connections are established through the medium of serially related 'automatic switches, and in which one 4of the switches in a series belong ing to a major group of the system may be omitted for the salie of economy at the initial installation without interfering with the use of a uniform4 numbering system laid out in accordance with the ultimate capacity.

The invention contemplates a telephone trunhing system employing an improved so called digit absorbing selector switch.

In accordance with the invention, a circuit arrangementis provided whereby the first set of impulses the selecto-r receives does not cause any movement of such selector but prepares the selector to respond to the next set of impulses from the sender, at the termination of vwhich it automatically hunts for an idle trunk. Thus, one of the digits in the telephone number of any line in a given group is eliminated so that the lines in such group may be reached by means of a smaller series of Switches than the lines in other groups.

Other features will appear from the detailed description.

In the drawings, Figure 1 is a schematic diagram of the trunking system, Vand Fig. 2 is a circuit diagram of the digit absorbing selector.

Fig. 1 shows the organization of a trunking system as applied to an automatic telephone system having a capacity of 100,000 lines and using the well-known Strowger vertical and rotary switches operated accordingv to the two-wire system of control. In a system of this size, the lines are usually distributed among a plurality of different offices, and t-he first selectors, which are the switches which respond to the lirst digit in called telephone numbers, may function as office selectors. Since there are ten levels in a selector switch, there may be ten different oli'ices and when a calling subscriber operates his dial to call the desired number, the first digit will operate the first or office selector to select the trunk line leading to the proper oii'ice, and theremaining digits will operate a second or incoming selector, a third selector and a connector, in the selected on'ice, to

complete the connection.

The .office which is reached when the digit 2 is dialed Fig. 1) as well as the other oliices inthe system with the exception of the one which is reached when the first dig'- it dialed in 3, for example, may be equipped to their full capacity, whilefor the purpose of illustration, it will be assumed that the oflice to which the connection is extended when the first digit dialed is 3, has vfor the time being,vno more than 1,000 telephone linesterminating in it.

In order to point out the trunking var rangement ,more clearly, it will be assumed that the subscriber at substation 1 desires to call the subscriber ,at substation -17 in which case the connection may beextended asfollows: from thesubstation 1 by way of the individualv line switch 2,-first or office selector 8, second or incoming selector 14, third or hundreds selector 15, andethe `vconnector 16, to the substation 17. This, it 4willbe noted,vis the usual trunking arrangement. Assuming, vnow that the subscriber at substation 1 calls the subscriber at thesubstation 7,

the connection may be traced as follows:`

from the substation 1 by yway of the individual line switch 2, first or office selector 3, third or incomingselector 5, and the connec tor' 6,v to the substation/7. This latter connection extends over a path similar tothe ,onevfor the substationv 17, with the exception that it does not pass through any second or thousands selector. It .is obvious in viewof the fact thatthere is only one thousands group of lines terminating in that oliice thatno' thousands selector is needed. only necessary to introduce an extra but ineffective digit into the number dialed, to

,make the telephone numbers in this office have the same number of digits as those in the other offices. This is accomplished in the system disclosed herein, by arranging the selector 5 so that after connection is obtained therewith, it will not make any ,selectiveoperation when the first digit is dialed, but

- willoperate like a regularselector vwhen the nextdigit is dialed. t

It is desirable to be ablenot only to. assign numbershaving the desired-,number vof digits but also tobe ableto assignnumbers that ymay be retained even atten the ,systemV .has

reached .its ultimate.,growtl1.

Now it As is well-known, a full 100,000 line system, may consist of a main office in which part of the lines terminate, and one or more other offices of probably 1,000 lines each.

k1n the present system this situation does not cause any difliculty to be encountered in numbering for future growth because with the digit absorbing selectors varranged to absorb the thousa-nds7 digit vregardless of what that digit is, the numbers` may be assigned not only in any thousands7 group of lines, but in each and every thousands7 group of lines.

The system havingl thus been described in :i more or less general manner, its operation will now be described in greater detail. For this purpose it will be assumed that the subscriber at substation 1 (Fig. 1) desires to talk with the subscriber at substation 7. lll hen the receiver is removed at substation 1, the individual line switch 2 is operated to extend the connection to an idle first or office selector in the manner well-known in the art. The first selector 3, in turn operates to extend the connection to an idle digit absorbing selector, and assuming that the digit absorbing selector 5 is the one to which the connection is extended, the wipers of the first selector switch 3 will connect with bank contacts 204, 205 and 205, (Fig. 2) and the following circuit is closed to operate relay 200; battery, right-hand winding of relay 200, 224, 225, 205, subscribers line and subtation, 204, 222, 221, left-hand winding of relay 200 to ground. Relay 200 operated, closes the following circuit to operate slowrelease relay 210; battery, relay 210, 201, 202, 231, 230 to ground. Relay 210, operated, connects ground to lead 206 to cause the selector to test busy to other first selectors over a circuit as follows: ground 214, 215 to lead 206. vThe selector switch is now ready to receive the series of impulses ordinarily corresponding to the thousands digit of the number dialed, and when the calling subscriber operates his calling device in accordance with the next digit of the desired number, the circuit of relay 200 is interrupted and relay 200 follows the impulses. When relay 200 releases, a circuit is closed to operate slow relay 240 as follows: battery, relay 240, 211, 212, 203, 202, 231, 230 to ground. Relays 210 and 240 are made slow-to-release to prevent them from releasing when relay 200 opens alternately, their respective holding paths, during the impulse period. When relay 240 operates, a circuit is closed to operate relay 270 as follows'. battery, relay 270, 251, 252, 243, 241, 215, 214 to ground. Relay 270 operated locks as follows: battery, relay 270. 258, 257, 273, 274, 282, 283, 291, 292, 215, 214 to ground. 1When the calling device returns to normal the series of impulses ceases, relay 200 remains operated, and opens at 203, the cirparticular p cuit through slow relay 240 which releases. lVhen relay 240 releases, a circuit is closed as follows to operate slow-to-operate relay 250; battery, relay 250, 2567 255, 271, 272, 242, 241, 215, 214 to ground. Relay 250 operated, opens at its contacts 257 and 253, the circuit through relay 270 which releases.

ARelay 250 operated, locks over a circuit as follows: battery, relay-,f 250, 256, 254, 215, 214 to ground. Thus, it willbe observed that the net result obtained at the end of the first train of impulses is that relay 250 is operated and locked, and the vertical magnet 290 Ais connected through contacts 260 and 261, in parallel with relay 240, but since no complete circuit has` yet been established for the vertical magnet 280, the selector brush rod 297, of which only a part is shown, carrying the brushes 217,218 and 219, has not moved from the normal position, hence the impulses corresponding to the thousands digit have been received and absorbed without moving the selector switch off' nprmal,

The calling subscriber now voperates his calling device, lin accordanccfwith the digit of the desired number and the series of impulses corresponding to the hundreds digit of the number is now dialed. Relay`200 follows the impulses as before, and operates slow relay 240 in the manner previously described. The vertical magnet 280 which is in parallel with relay 240 also operates,

and follows the impulses set up by relay 200. The first time the vertical magnet operates, it raises the selector rod 297, of which Y only a part is shown, sufiiciently to close the contacts 290 and 291, 293 and'294, 295 and 296, thus closing the circuit to operate relay 270 as follows: battery. relay 270, 290, 291, 253, 252, 243, 241, 215, 214 toground.

Relay 270 operated, locks as follows: battery, relay 270, 290, 291, 233, 232, 274. 273,?

257, 259, 231, 230 to ground. lachtinie the vertical magnet 230 operates, the selector rod 297 carrying the brushes 217, 218 and 219, advances one step in the manner well-known in the art, until when the impulses cease. the brushes 217, 218 and 219 are in the proper position to engage with the terminals of the first trunk in the selected level, as soon as the rotary magnet 231. operates as hereinafter described. When the series ofimpulses ceases, relay 240 releases as before, and a circuit is closedrto operate the rotary magnet 281 as follows: battery, magnet 281, 295, 296, 271, 272,242, 241, 215, 214, to ground. Magnet 281 operated, opens at 232 and 233, the circuit through relay 270. and causes the selector rod 297 to rotate and advance the brushes 217, 218 and 219 to the terminals of the first trunk in the levelselected. if the first trunk in the group is busy, ground will be connected to the terminal 299 and when the rotary magnet- 231 releases, a circuit will be closed to operate relay 270 as follows: battery, relay 270, 290, 291, 283, 282, 229, 228, 209, 219, 299 to ground. Relay 270 operated, closes the circuit previously described tooperate magnet 281,A thus causing relay 270 to release and the selector rod 297 to rotate another step and carry brushes 217, 218 and 219 to the terminals associated with the next trunk in the group. This cycle of operation continues until an idle trunk is found. When an idle trunk is found, ground will not be connected to its terminal 299, hence relay 270 will notreoperate, but a circuit will be closed to operate relay 220 as follows: battery, relay 270, 29o, 291, 28s, 282, 22o, 215, 214, to ground. Relay 220 has been previously shunted out by ground at 280 or 219. Due tothe high resistance of relay 220, relay 270 will not operate. Relay 220 operated, releases relay 200, connects lead 204 to brush 217 by way of 222, 22,3 and 207, lead 205 to brush 218 by way of 225, 226 and 208, and lead 20G to brush 219 by way of 227, 228 and 209. The calling subscribers line is now extended by way of brushes 217 and 218 to the connector 6, and ground from the connector circuit is connectedto brush 219 to cause the seized trunk to test busy. Relay 220 locks over the following circuit: battery, relay 270, 290, 291, 28s, 282, 22o, 227, 22s, 209, 219 to ground. Relay 250 remains locked in parallel with relay 220 to ground at brush 219. Relay 200 released, releases relay 210, but the latter being slow-to-release will remain operated long enough for relay 220 to lock before its operating circuit is opened at 215 by the release of relay 210.

The circuit will be extended to the called station by means of connector 6 in the manner well-known in the art.

l,"Vhen the lcalling subscribers receiver is replaced on the switchhool, ground-will be removed from the brush 219, and relays 220 and 250 will release, and the release magnet 284 will operate as followsgbattery, release magnet 284, 294, 29e, 213, 212, 20e, 202, 231, 230, to ground. Then the release magnet 284 operates, the selector rod 297 releases and restores to normal, thus opening at 294 the circuit through the release magnet 284, which releases.

While the digit absorbing selector shown in Fig. 2 has, for purposes of illustration, been used as an incoming selector in a 1,000 line oce to absorb the thousands digit, it is not so limited, but may be substituted'for any selector switch in a series in an automatic telephone system, as conditions may dictate.

lVhat is claimed is:

1. In a digit absorbing selector having a primary movement in response to more than one series of impulses and an automatic secondary movement, means for dissipating the iirst series of impulses, a relay, a circuit ,for

operating said relay after the rst series of impulses received by said selector has been dissipated, a magnet, and a circuit controlled by said relay for closing the circuit of said magnet so that the subsequent series of impulses will initiate the primary movement of the switch.

2. In a telephone system, a subscribers line having an impulse sender at the substation, a selector, a circuit including said sender leading to the selector, an operating magnet for said selector', means in the selector for absorbing a series ot impulses from said sender without operating said magnet to move the selector from normal, a relay, and means responsive to the completion ot the absorbed series of impulses tor energizing said relay to render said magnet responsive to the next series of impulses.

3. In a telephone system, a telephone line having an impulse sender at the substation thereof, an automatic swltch, a circuit including said sender and extending to the automatic switch, an operating magnet for said switch, means in the switch or dissipating a series of impulses transmitted thereto by said sender without operating said magnet to move the switch from its normal position, a relay, means eliective at the end of the dissipated series of impulses for closing an energizing circuit for said relay to prepare a circuit for said magnet, and means for operating the magnet in this circuit in response to the next series ot impulses.

4. In combination, a subscribers line having an impulse transmitter at the substation thereof, a selector switch, means for extending said line to said switch, an operating magnet and a control relay for said switch, means in said switch for absorbing the rst series of impulses transmitted thereto by said transmitter without operating said magnet to move the switch "rom normal, means responsive to the completion ofthe first series for energizing said relay, and means controlled by said relay in its energized condition for rendering said magnet responsive to the next series ot impulses. v

5. The combination in a telephone system of a telephone line having a sender at the substation, a selector switch, means for extending said line to'said switch, an operating magnet for said switch, a control relay, a second relay, means responsive to a series ot impulses sent to said selector tov operate the control relay without operating said magnetl to move the selector, a circuit closed by said control relay responsive to the completion of said series otl impulses to cause the operation of said second relay to prepare a circuit for said magnet, and means responsive to thenext series vof impulses transmitted to the switch for operating said magnet.

6,. In a telephone exchange system, a calliiig line ii'ziving cui :impulse Sender zit. the SubStutiou thereof, zi plurality of groups of culled lilies, the directory uuu'ibers ot uil Laid lirios having the saine number of' digits7 :i series of switches 'for auch group for exieridiug tire ceiling iiiie to zi, eziiied line there iii some o if lSuid serieu iuiif'ing :i ieSs number ot switches thun others, :in operating iii-iiguet am] u control relay for certain oi.' sind r-witciieii, iiieiiiifs in euch of siiidlzitter switches tor :ibfioroing u series oit iu'ipuisefi when 4r .l 'Ui t i. ,A l irl x y tmoiiiuiired t ieicio by sind be dei wir, iouu loperzii'fiiig.; the muguet to more tile Switch trom iioi'iuiii menus Vtor operutiug the coutroi reifiy riisriouiiiro to the ei'iiupie ioii o'f the :ibiioriimi ir-ries to prepure :i rircuit for the opeiiiiiiig iiisigiut :uid menus responsive to the next seriee oi. nipuiiiis Sent to the Switch 'tor actuating the magnet iii the brepured.

circuit 'to advance the switch.

7. in im exeuzmge Hysteria, zi, culling iiue, two groups ol eil-Hed linee, uit iiuviiig direitor)7 numbers with the mime number ot dig'- i l i x. i rus, a series comprising a Certain number o without 'operating the stepping muguet,V

uio-.imi responsive to the completion o'r'rf' the diiisiipiited i-lerieFi for energizing sind relay 'to propere ii, circuit ior Said muguet, and

Sipa-tiiig a `Series of 1 mesi-iis respoiisivr-to u Subsequent series of impulses for :ultuatingA Suid n'izigiiet 'iii the prepared circuit to :uivzauoe the Switch. v Y

in te i'iony whereof, we have Signed our mui'ieg to this specification October, 19223.

FRrEND.

Diiisrrru.l

OTTO A. GEORGE this 22 day of 

